I have been thinking recently about how to represent "special lanes"
in OSM. I have been working on a flexible scheme for this which I am
calling "lane groups". Below is my current draft...If there is any
support out there I will turn it into a wiki-page and get the ball
rolling. All comments are welcome!
lanegroup tag
In order to support the construction of spoken navigation instructions
and "junction view" functionality it will be necessary to indicate how a
road is divided into (groups of) lanes and how these lanes are designated.
By grouping the lanes of traffic into groups, the characteristics of
each group of lanes can be tagged, without having to define each lane as
an individual way or having to define junctions as complex relations.
The idea is to create a simple, pragmatic but effective way of recording
the information into the database, without creating a substantial
workload for mappers.
One-way ways
The lanegroups are numbered from left to right, irrespective of whether
one "drives on the left" or not. So in the UK (driving on the left), at
a simple motorway exit, lane group 1 would be the lanes to take the
exit, and lane group 2 would be the lanes to continue on the motorway.
At a similar motorway exit driving on the right, lane group 1 would
continue straight on and lane group 2 is for taking the exit.
Two-way ways
Lanegroups are once again numbered from left to right *as seen from the
"forward" direction of the way*. An approach to a cross-roads with
dedicated lanes for turning left and right (in the UK) would therefore
have (in the forward direction of the way) lanegroup 1 for turning left,
lanegroup 2 for straight on, lanegroup 3 for turning right, and
lanegroup 4 for the opposite direction. If the junction was symmetrical,
approaching the same junction from the opposite direction (now in the
reverse direction of the way) would have lanegroup 1 for the opposite
direction, lanegroup 2 for turning right, lanegroup 3 for straight on
and lanegroup 4 for turning left.
Tagging
All tags are to be applied to the Way only.
Information related to the lane group could include:
* number of lanes
* direction as related to the "direction" of the way
* intended direction
* access restrictions for certain vehicle classes (this can cover
dedicated bus lanes etc)
* access restrictions for certain times of day (this covers special
rush-hour-only lanes)
* signage
There is currently no way to have a list of subtag values other than
key=value1;value2;value3 etc.
As the number of lanegroups will in practice not exceed four or five I
suggest using simply lanegroup1, lanegroup2 etc.
Example - motorway exit, driving on left
highway=motorway
oneway=yes
lanes=2
lanegroup1:lanes=1
lanegroup1:intention=exitleft
lanegroup1:signage=A1234;Town Centre
lanegroup2:lanes=2
lanegroup2:intention=straighton
lanegroup2:signage=M1;The North
Example - urban crossroads, driving on left, no left turn for HGVs
highway=primary
oneway=no
lanegroup1:lanes=1
lanegroup1:intention=turnleft
lanegroup1:hgv=no
lanegroup2:lanes=2
lanegroup2:intention=straighton
lanegroup3:lanes=1
lanegroup3:intention=turnright
lanegroup4:lanes:2
lanegroup4:direction=reverse
Note that I do not intend this to be used for routing as such. There are
already methods of indicating turn and access restrictions etc.
Lanegroups are to form a basis for "junction view" type applications.
Editor support
It would be nice if the OSM editing applications were to support
lanegroups. One action which would benefit from support is reversing a
two-way way's direction - which would affect the numbering of the
lanegroups.
Further work
For best effect it would be nice if we could arrive at a consensus on
the two subtags which are really new, namely "intention" and "signage".
To kick things off I would like to suggest the following:
intention
mergefromleft (for traffic joining from left)
turnleft (more or less 90 degrees)
exitleft (shallow angle)
straighton
exitright (shallow angle)
turnright (more or less 90 degrees)
mergefromright (for traffic joining from right)
signage
line1;line2; etc
possibly a way of identifying the road number, such as wrapping
it in some kind of brackets, e.g. [A123], so it can be displayed with
suitable emphasis
Also the relationship of the main "lanes" tag to the lane groups should
be explicitly defined. I suggest that it contains the number of
"through" lanes only, so a typical motorway will have lanes=2 or lanes=3
for most of its length, with the lanegroups being used for occasional
extra lanes for the exits.
On 04/07/2010 22:41, Alan Millar wrote:
How are people using the "lanes" tag on motorways? Do you count the
on/off ramps that come and go?
On a lot of the freeways near me, they have two main driving lanes on
each direction, so I set it up as a dual carriage way with one-way on
each side, and mark each side as lanes=2.
The question comes in for the on/off ramps. There are sections where
two intersections are somewhat close together, and so there is an
on-ramp, a long extended merging lane, then the next off ramp.
Strictly speaking, there is a third lane for some distance between the
the ramps, but it isn't a "through" lane. There are only 2 driving or
through lanes in that section of freeway.
See for example hwy 217 between Denney and Allen at:
http://www.openstreetmap.org/?lat=45.473345&lon=-122.786743&zoom=18&layers=B000FTT
I have only been counting the driving or through lanes, so I have
tagged this as lanes=2, and just ignored the short extent of the extra
merging lane.
Likewise, there are suburban streets that have an extra turn lane just
before an intersection, like Murray Blvd at:
http://www.openstreetmap.org/?lat=45.4814&lon=-122.8261&zoom=18&layers=B000FTTT
As one big street with two driving lanes each direction, I've tagged
it as lanes=4 and ignored the short extent of the extra turn lane.
And one more variation is the suburban boulevard with one center lane,
only allowed to be used for turning/merging in and out of driveways.
I consider this like the freeway merging lanes; I've just been
counting the driving lanes and not the turning lane also. See Canyon
Road at:
http://www.openstreetmap.org/?lat=45.489479&lon=-122.799664&zoom=18&layers=B000FTTT
So, is this what other people are doing? Any pros/cons to handling to
merging and turn lanes like this?
Thanks
- Alan
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